Merge "Support for loading Guice modules from /lib"

Documentation/config-gerrit.txt

@@ -1997,6 +1997,23 @@ By default unset, as the HTTP daemon must be configured externally
 by the system administrator, and might not even be running on the
 same host as Gerrit.
 
+[[gerrit.installModule]]gerrit.installModule::
++
+Repeatable list of class name of additional Guice modules to load at
+Gerrit startup and init phases.
+Classes are resolved using the primary Gerrit class loader, hence the
+class needs to be either declared in Gerrit or an additional JAR
+located under the `/lib` directory.
++
+By default unset.
++
+Example:
+----
+[gerrit]
+  installModule = com.googlesource.gerrit.libmodule.MyModule
+  installModule = com.example.abc.OurSpecialSauceModule
+----
+
 [[gerrit.reportBugUrl]]gerrit.reportBugUrl::
 +
 URL to direct users to when they need to report a bug.

gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/SiteProgram.java

@@ -24,6 +24,7 @@ import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.metrics.DisabledMetricMaker;
 import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.metrics.dropwizard.DropWizardMetricMaker;
+import com.google.gerrit.server.LibModuleLoader;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.GerritServerConfigModule;
 import com.google.gerrit.server.config.SitePath;
@@ -180,6 +181,7 @@ public abstract class SiteProgram extends AbstractProgram {
     modules.add(new SchemaModule());
     modules.add(cfgInjector.getInstance(GitRepositoryManagerModule.class));
     modules.add(new ConfigNotesMigration.Module());
+    modules.addAll(LibModuleLoader.loadModules(cfgInjector));
 
     try {
       return Guice.createInjector(PRODUCTION, modules);

gerrit-server/src/main/java/com/google/gerrit/server/LibModuleLoader.java

@@ -0,0 +1,64 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server;
+
+import static java.util.stream.Collectors.toList;
+
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.inject.Injector;
+import com.google.inject.Key;
+import com.google.inject.Module;
+import com.google.inject.ProvisionException;
+
+import org.eclipse.jgit.lib.Config;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.List;
+
+/** Loads configured Guice modules from {@code gerrit.installModule}. */
+public class LibModuleLoader {
+  private static final Logger log =
+      LoggerFactory.getLogger(LibModuleLoader.class);
+
+  public static List<Module> loadModules(Injector parent) {
+    Config cfg = getConfig(parent);
+    return Arrays.stream(cfg.getStringList("gerrit", null, "installModule"))
+        .map(m -> createModule(parent, m))
+        .collect(toList());
+  }
+
+  private static Config getConfig(Injector i) {
+    return i.getInstance(Key.get(Config.class, GerritServerConfig.class));
+  }
+
+  private static Module createModule(Injector injector, String className) {
+    Module m = injector.getInstance(loadModule(className));
+    log.info("Installed module {}", className);
+    return m;
+  }
+
+  @SuppressWarnings("unchecked")
+  private static Class<Module> loadModule(String className) {
+    try {
+      return (Class<Module>) Class.forName(className);
+    } catch (ClassNotFoundException | LinkageError e) {
+      String msg = "Cannot load LibModule " + className;
+      log.error(msg, e);
+      throw new ProvisionException(msg, e);
+    }
+  }
+}

gerrit-war/src/main/java/com/google/gerrit/httpd/WebAppInitializer.java

@@ -31,6 +31,7 @@ import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.lucene.LuceneIndexModule;
 import com.google.gerrit.metrics.dropwizard.DropWizardMetricMaker;
 import com.google.gerrit.pgm.util.LogFileCompressor;
+import com.google.gerrit.server.LibModuleLoader;
 import com.google.gerrit.server.account.InternalAccountDirectory;
 import com.google.gerrit.server.cache.h2.DefaultCacheFactory;
 import com.google.gerrit.server.change.ChangeCleanupRunner;
@@ -339,6 +340,7 @@ public class WebAppInitializer extends GuiceServletContextListener
     });
     modules.add(new GarbageCollectionModule());
     modules.add(new ChangeCleanupRunner.Module());
+    modules.addAll(LibModuleLoader.loadModules(cfgInjector));
     return cfgInjector.createChildInjector(modules);
   }